Larger microturbines make inroads in industrial cogeneration

Microturbines have come a long way. These distant descendants of aviation auxiliary power supply turbines and automotive turbochargers were first developed in the 1990s. From the beginning, they have been recognized as an important technology for on-site electric generation. Beneficial use of the turbine waste heat has always been the key to successful installations.

04/01/2010

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Microturbines have come a long way. These distant descendants of aviation auxiliary power supply turbines and automotive turbochargers were first developed in the 1990s. From the beginning, they have been recognized as an important technology for on-site electric generation. Beneficial use of the turbine waste heat has always been the key to successful installations. T

he first cogeneration microturbines were in the 25-30 kW size range, followed by later developments of the 60-65 kW size class. In recent years, manufacturers have introduced larger 200-250 kW microturbines, which makes this technology more attractive for commercial and industrial users.

Making Full Use of the Energy

The larger microturbine generators have fuel-to-electricity efficiencies of 25 to 30% — slightly lower than larger utility class gas turbines. However, this doesn't take into account the fact that virtually all microturbine installations are designed to also use the high-temperature turbine exhaust in a wide range of useful applications. This can bring the overall thermal efficiency of the installation up to 75 to 80%, and makes the on-site generation package an attractive energy solution.

Capstone Turbine Corporation is a major supplier of microturbines, offering units in the 30kW, 60kW and 100kW classes, as well as the C200, a new 200kW product that is especially attractive to industrial and large commercial customers. According to Kyra Bonavida, a spokesperson for Capstone, “Companies that have various thermal needs that can be satisfied or assisted by the microturbine waste heat are often interested in microturbine power systems.” She notes, “Mid-sized microturbines are a good source of energy for industrial facilities because they are efficient, clean, low maintenance, and can be easily connected to the utility grid.”

Many Ways to Use Byproduct Heat

Bonavida cites as examples of byproduct heat utilization the production of hot water for food processing and for drying tasks in the furniture industry. Other Capstone installations include process heat in the plastics and plating industries, generation of steam for sterilization and drying operations, and preheating air for use in industrial burners such as found in the metals industry.

Bonavida also points out that hot water or steam can be used for cooling needs. “The waste heat can be run through absorption chillers to provide cooling for facilities such as data centers or other facilities that have refrigeration requirements.” The recently introduced Capstone C200, because of its larger scale, triples the amount of byproduct heat energy from a single unit, making it more attractive for the industrial market. Capstone also offers an engineered package of five C200 units that has an electric capacity of 1MWe, and a proportionately larger heat output.

Can Use Methane Generated On Site

Another way in which microturbines are a good fit for industrial applications is that they can use byproducts from other manufacturing operations to fuel the turbine. As an example, digesters or other processes that produce methane can feed that fuel into the microturbine as a stand-alone fuel or as a supplement to natural gas. Bonavida notes, “For example, wastewater treatment facilities can use the methane byproduct to fuel the microturbine.” This application is already being used by several municipalities.

For industries that have concerns about emissions, the larger microturbines are also attractive. According to Bonavida, the Capstone C200 is CARB certified for emissions. “This makes it extremely easy to get the equipment and site approved and it often does not even require an air permit. The C200 is also UL certified, which makes it easy to get building permits for installing the equipment. The UL certification also makes connecting to the grid a simpler procedure.”

Ingersoll Rand Mid-sized Offering

Another major provider of microturbines in the 200%%MDASSML%%250 size class is Ingersoll Rand. This global firm offers its Model MT250, a 250 kW machine that is well adapted to industrial applications. Andy Freeman from this company provided information on this product at a Technology Marketing Assessment Forum (TMAF) sponsored by the Energy Solutions Center in Pasadena in spring, 2009. In his presentation he noted, “This technology makes sense for companies that have a 24/7 electrical load greater than 250 kW, and a 24/7 need for hot water.”

Freeman pointed out that these units are especially attractive in areas where there are high electric rates. He adds, “In some cases there are also incentives available from the utility for an industrial microturbine installation.” Freeman points out that the maximum use of the byproduct heat is essential for a good microturbine application.

Compact Design Saves Space

The MT250 includes a patented recuperator and an integrated heat recovery system to minimize the amount of floor space needed for the installation. The package is CARB-2007 certified for use in California and features NOx emissions of less than 9 ppm. The unit requires only one planned annual shutdown and the overhaul interval is 40,000 hours, or nearly five years of operation.

Chocolate Plant Chooses Microturbines

An example of a successful industrial installation of microturbines with heat recovery is an installation at Astor Chocolate in Lakewood, New Jersey. In 2006, Astor was looking for an energy solution that would offer high power supply reliability as well as effective heating and cooling. The installation features five Capstone C60 microturbines with integrated heat recovery. The hot water supplements the plant's hot water and space heating requirements, and also feeds a 100-ton absorption chiller for building cooling, including cooling for the finished chocolate products in the warehouse.

According to Astor Chocolate's Plant Engineering Manager, Joe Verschleisser, “We installed these Capstone turbines to enhance our already developed cogeneration design and to go further green with the latest technology.” He explains that the turbines are operated in a load-following capability due to New Jersey's lack of net metering functionality. The company has been pleased with the results of the installation. Verschleisser says, “The Capstone microturbines have paid for themselves and proven to be dependable and reliable.”

Microturbine Cogeneration Makes Sense

If your plant needs reliable cogeneration and has use for the considerable heat output of a mid-sized microturbine, this may be a solution worth investigating. The obvious attraction is the high-efficiency use of natural gas for electric generation, heating and cooling in an installation that makes full use of the energy.

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